Allyl phenols



Patented Sept. 1, 1970 3,526,668 ALLYL PHENOLS William H. Starnes, Jr.,and Tad L. Patton, Baytown, Tex., assignors to Esso Research andEngineering Company No Drawing. Filed Oct. 2, 1967, Ser. No. 671,975Int. Cl. C07c 39/18 U.S. Cl. 260624 13 Claims ABSTRACT OF THE DISCLOSUREAn allylated phenol substantially free of allylaryl ether is obtained bycontacting an alkali metal salt of a 2,6- disubstituted phenol with aprimary allyl halide in a solvent.

BACKGROUND OF THE INVENTION Field of the invention The present inventionis directed to allylation of phenols. More particularly, the inventionis concerned with allylation of phenols to obtain an allyl phenolsubstantially free of allylaryl ether. In its more specific aspects, theinvention is concerned with a method of preparing allylated phenolemploying a solvent to produce allylated phenols and recovering theallylated phenol.

Description of the prior art Heretofer, nuclear allylation of phenolshas been accompaned by attack by the allylating agent upon the phenolichydroxyl group with resultant formation of considerable amounts of thecorresponding allylaryl ethers. Allyl phenols have been produced by theClaisen rearrangement, but prior to the present invention2,6-disubstituted allyl phenols in which the allyl moiety is attached tothe ring by an unsubstituted allylic methylene group were not readilyobtainable.

SUMMARY OF THE INVENTION The present invention may be briefly describedand summarized as involving a method of producing allyl phenols in whichan alkali metal salt of a 2,6-disubstituted phenol, preferably a2,6-di-t-alkylphenol, is contacted in a solvent, preferably a highlypolar aprotic solvent, with a primary allyl halide to form a productcontaining allylated phenol substantially free of allylaryl ether.

DESCRIPTION OF THE PREFERRED MODES The present invention may beillustrated by the reaction according to the following equation:

and 2,6-dicyclohexylphenol.

The allyl halides used in the present invention include the allyliodides, chlorides, and bromides. Allyl chlorides and bromides arepreferred. Examples of suitable allyl halides include: allyl bromide,allyl iodide, allyl chloride, 1-bromo-3-methyl-but-2-ene, and1-chloro-5,5,7,7- tetramethyl-oct-Z-ene.

The organic solvent employed in the present invention may suitably be amono-cyclic aromatic hydrocarbon such as but not limited to benzene,ethylbenzene, toluene, xylene, and the higher members of the homologusseries but, preferably, a highly polar aprotic solvent such as but notlimited to dimethylformamide, dimethylacetamide, N-methylpyrrolidone,hexamethylphosphoramide, and similar organic nitrogen-containingsolvents.

The allyl phenols of the present invention have 3 to 12 carbon atoms inthe allyl group and are useful as oxi dation inhibitors. Particularly,the allyl phenols are useful in inhibiting oxidative attack on solidpolymers of alpha mono-olefins such as polyethylene and polypropylene;solid copolymers of alpha monoolefins may also be stabilized againstoxidative attack. The allyl phenols may be used to inhibit oxidation ofgasoline, jet fuel, natural and synthetic rubber, vegetable fats andoils, and the like.

Temperatures employed in producing the allyl phenols may range fromambient temperatures to reflux temperatures to reflux temperatures ofthe reaction mixture which may range from about 25 to about 300 C.

The alkali metal salt of the dialkylphenol and the allyl halide aresuitably used in a molar ratio from about 1:1 to about 1:20, preferably1:1.1, and the molar ratio of solvent to alkali metal salt may vary fromabout 1:1 to about 20:1, preferably 5:1, when the solvent isdimethylformamide.

The allyl phenol may be suitably recovered from the reaction product bysolvent fractionation, solvent precipitation, drying, washing withsolvents and the like, fractional distillation, gas chromatographicseparation, or by a combination of two or more or all these techniquesor by other well known separation methods.

In the several examples, the abbreviation NMR signifies nuclear magneticresonance and G.C. signifies gas chromatographic.

EXAMPLE 1 A solution of 2,6-di-t-butylphenol (41.4 g., 0.201 mole) in200 ml. anhydrous methyl alcohol was placed in a 3-necked flaskprotected from moisture and fitted with a dropping funnel, nitrogen gasinlet, stirrer, and a condenser attached for distillation. The air inthe flask was replaced with nitrogen, and a solution of sodium methoxide(10.8 g., 0.200 mole) in50 ml. anhydrous methanol was added. Themethanol was removed by distillation. Then 400 ml. dry benzene was addedto the residue and distillation continued to remove methanol. This wasrepeated again to remove the last traces of methanol. T hen 400 ml.benzene was added to the dry salt and the distillation attachmentreplaced by a reflux condenser.

To the stirred suspension was added allyl bromide (48.3 g., 0.399 mole),and the mixture was stirred and heated at reflux temperature overnight.The mixture was then cooled and washed with water to remove all the saltformed during the reaction. After drying over anhydrous magnesiumsulfate, the benzene was removed and the residue distilled. Twenty-onegrams of unreacted 2,6-di-tbutylphenol were collected at 78-84 C./0.2mm. The desired product was in the fraction collected at 8890 C./0.2 mm.This fraction weighed 17.3 g.; G.C. analysis showed it contained 34.8%of the desired product. Therefore, the yield of desired product was 12%,based on starting phenol, or 25 based on phenol consumed in thereaction. A nuclear magnetic resonance spectrum confirmed the structure(4-allyl-2,6-di-t-butylphenol).

3 EXAMPLE 2 Sodium methoxide (11.8 g., 0.218 mole) was suspended in 200ml. dry dimethylformamide. A solution of 2,6-dit-butylphenol (41.2 g.,0.200 mole) in 100 ml. dimethylformamide was added, and the cleargreen-colored solution was stirred for one hour. Then allyl bromide (25g., 0.21 mole) was added during a -minute period with vigorous stirring.Heat was evolved, and the temperature rose to 56 C. The reaction mixturewas allowed to cool slowly to room temperature where it remainedovernight. It was then poured into one liter of ether to precipitatesodium bromide, filtered, washed with ether, and dried. The sodiumbromide weighed 20.35 g. (95.5% of theory). The filtrate was washed withwater to remove dimethylformamide and dried over sodium sulfate.Evaporation of the ether left a residue whose major constituent (about75%) was shown by NMR analysis to be the desired product. Duringdistillation fractions were collected at 90100 C./0.2 mm. (2.5 g.),100-103 C./0.2 mm. (11.1 g.), and 103 C./0.2 mm. (27.5 g.). The residueweighed 2.1 g. The fraction collected at 103 C./ 0.2 mm. was pure4-allyl-2,6-di-t-butylphenol (56% yield).

EXAMPLE 3 The sodium salt of 2,6-di-t-butylphenol was prepared by invacuo evaporation to dryness of a solution of 9.32 g. (0.0452 mole) ofthe phenol and 2.70 g. (0.0500 mole) of sodium methoxide in 50 ml. ofreagent grade methanol. The residue was quickly dissolved in 50 ml. ofanhydrous dimethylformamide under nitrogen, and the solution was stirredwhile 7.45 g. (0.0500 mole) of 1-bromo-3-methylbut-2-ene was added overa 10-minute period. During the addition the temperature rose to 51 C.,and a white solid (presumably sodium bromide) appeared. After stirringovernight at ambient temperature under nitrogen, the mixture was warmedat 9197 C. for one hour, cooled, and diluted with 250 ml. of water. Thesolution was then extracted with four 100 ml. portions of ether; thesewere combined, washed in succession with three 100 ml. portions of 10%hydrochloric acid and three 75 ml. portions of 3 N sodium carbonate,dried with Drierite, and evaporated to give a residue (11.37 g.) whichwas shown by NMR analysis to contain a considerable amount of pallylatedphenol (amixture of isomers). Fractionation at reduced pressure failedto give satisfactory separation; however, the material with B.P. 164 C./10 mm. proved to be essentially pure 2,6-di-t-butyl-4-(3-methyl-2-buten-1-yl)phenol (1.14 g., 9% yield). Analysis of the lowerboiling fractions(B.P. 1l5-152 C./10 mm.) by NMR showed that they also containedconsiderable amounts of this product. Redistillation of the materialboiling at 164 C./ 10 mm. gave a pure sample whose structure wasrigorously proven by elemental analysis and by NMR, mass, and infraredspectral measurements.

EXAMPLE 4 A solution of 2,6-di-t-butylphenol (41.2 g.; 0.2 mole) in 100ml. dry dimethylformamide was added to a stirred solution of sodiummethoxide (11.8 g.; 0.22 mole) in 200 ml. dry dimethylformamide in anitrogen atmosphere. After stirring one hour to allow formation of thesodium salt of the phenol, freshly distilled1-chloro-5,5,7,7-tetramethyl-2-octene (42.4 g.; 0.21 mole) was added.

After stirring 3 hours at room temperature, there was no evidence ofreaction. The mixture was then heated at 60 C. for 9 hours. The greencolored suspension was diluted with 2 volumes of ether. The suspensionwas then washed with water to remove sodium chloride and thedimethylformamide. The ether phase was washed successively with 2%hydrochloric acid and water. After drying the ether extract overanhydrous magnesium sulfate, evaporation of the solvent left 67.8 g. ofa light yellow-colored oil.

G.C. separation yielded several small fractions and one major fraction.The major fraction represented 53.8%

4 of the total. The nuclear magnetic resonance spectrum showed that itwas 2,6-di-t-butyl-4-(5,5,7,7-tetramethyl- 2-octenyl)phenol. Therefore,the yield was 36.4 g., (47.7%).

EXAMPLE 5 The allyl phenol, 2,6-di-t-butyl-4-(5,5,7,7-tetramethyl-2-octenyl)phenol (DBDDP) produced in accordance with Example 4 was addedto solid polypropylene and the mixture tested to determine theeffectiveness of DBDDP as an antioxidant. Pelletized polypropylenecontaining DBDDP was subjected to contact with an oxygen-containingatmosphere at C. until failure (occurrence of noticeable degradation)along with speciments containing commercially available inhibitors inidentical amounts.

The results of these operations are shown in Table I.

TABLE I Compound Days to failure at 100 C. DBDDP 55 Ionol (average) 8Polygard (average) 8 1 0.1 wt. percent in polypropylene.

Ionol is 2,6-t-butyl-p-cresol.

Polygard is a triaryl phosphite used commercially as an antioxidant.

The date in Table I demonstrate that DBDDP is superior to both Ionol andPolygard as an inhibitor for polyolefins against oxidative attack.Hence, the present invention is quite useful and has unobviousproperties in that unexpected superior results are obtained.

When used as an oxidation inhibitor, particularly in solid polyolefinssuch as polypropylene and the like, the allyl phenol maybe used inamounts from about 0.01 to about 1.0% by weight based on the polyolefin.

While the invention has been described and illustrated by batch andbench scale reactions, it is to be understood that the invention may beconducted in a continuous operation.

The nature and objects of the present invention having been fullydescribed and illustrated and the best mode contemplated set forth, whatwe wish to claim as new and useful and secure by Letters Patent is:

1. Allyl phenol having a structure represented by th' formula:

where R and R are t-butyl substituents and R is a primary allyl grouphaving 3 to 12 carbon atoms.

CH3 where R and R are t-butyl.

CHZCH OHCI-IQC(CH )zCH2C(CH )gCH where R, and R are t-butyl.

6 4. A method of producing allyl phenol which consists 9. A method inaccordance with claim 4 in which the of: allyl halide is1-chloro-5,5,7,7-tetramethyl-oct-Z-ene.

contacting an alkali metal salt of a 2,6-disubstituted 10, A h d i danith claim 4 in which:

phenol selected from the group consisting of (a) the disubstitutedphenol is 2,-6-di-t-butylphenol; t-butylphenol, 2,6-di-t-pentylphenol,2,6-di-t-octyland phenol, and 2,6-dicyclohexylphenol with a primary (b)the solvent is dimethy1formamide allyl halide selected from the groupconsisting of allyl bromide, allyl iodide, allyl chloride, l-bromo-3-methy1-but-2-ene, and 1-chloro-5,5,7,7-tetramethyloct-2-ene in a molarratio from about 1:1 to about 1:20 in an organic solvent selected fromthe group consisting of benzene, ethylbenzene, toluene, xylene,

11. A method in accordance with claim in which the allyl halide is anallyl bromide.

12. A method in accordance with claim 10 in which 10 the allyl halide isan allyl chloride.

13. A method in accordance with claim 4 in which the dimethylformamide,dimethylacetamide, N-methyl S1vent is benzena' pyrrolidone, andhexamethylphosphoramide, the molar ratio of solvent to alkali metal saltbeing about 1 References cued 1:1 to about :1 at a temperature withinthe range UNITED STATES PATENTS from about to about 300 C. to form aproduct 2 681 371 6/1954 Gaydash containing the corresponding2,6-disu'bstituted p-allyl 2968679 6/1961 Aelony 260*624 phenol in whichthe allyl moiety is attached to the u phenol ring by an unsubstitutedallylic methylene 20 3198842 8/1965 Bemgan u 260 624 group, whichproduct is substantially free of allylaryl OTHER REFERENCES ether and 3Barner et al.: Chem.-Abs. 55 (1961), pp. 2540-41. recovering saidallylated phenol from the product. I c 5. A method in accordance withclaim 4 in which the Koflyarevsku et Chem 54 (1960) 6607' solvent isdimethylformamide. 25

6. A method in accordance with claim 4 in which the BERNARD HELFINPnmary Exammer t-alkyl phenol is 2,6-di-t-butylphenol. LOWE, AssistantExaminer 7. A method in accordance with claim 4 in which the allylhalide is allyl bromide. mg C] 8. A method in accordance with claim 4 inwhich the allyl halide is 1-bromo-3-methyl-but-2-ene. 44*775 252 4045896

